Interpretive Summary: Infections by the single celled parasite, Toxoplasma gondii are widespread in humans and livestock. It causes mental retardation and loss of vision in children. Humans become infected by ingesting uncooked meat infected with Toxoplasma or by ingesting food contaminated with feces of infected cats. Pigs are considered the most important meat source of Toxoplasma for humans sin the U.S. Cats are the only host that can directly transmit this parasit to pigs. Recent epidemiological evidence indicated cats are the main source of infection for pigs in Illinois. Scientists at the Beltsville Agricultural Research Center and the University of Georgia, Athens found a very low (0.9%) prevalence of T. gondii antibody in 1264 feral pigs from a remote island in Georgia lacking cats, compared with an 18% prevalence in 170 feral pigs from the mainland of Georgia. These findings support the role of the cat in the epidemiology of toxoplasmosis. These findings will be of interest to public health workers, veterinarians and wildlife biologists.

Technical Abstract:
Serum samples from 1,264 feral pigs from Ossabaw Island, Georgia were initially screened for antibodies to Toxoplasma gondii by the modified agglutination test (MAT) using whole-formalinized tachyzoites and mercaptoethanol. Seropositive samples were also tested by the Sabin-Feldman dye test, the latex agglutination test (LAT), and the indirect hemagglutination test (IHAT). Ossabaw Island is a remote, barrier island located southeast of Savannah, Georgia. Antibodies to T. gondii were found in 11 (0.9%) of 1,264 pigs. The antibody titers were 1:20 (1 pig), 1:80 (2 pigs), 1:160 (2 pigs), 1:320 (4 pigs) and 1:640 (2 pigs) by the MAT, and 1:8 (2 pigs), 1:16 (3 pigs), 1:32 (1 pig), 1:64 (2 pigs), 1:120 (1 pig) and >1:256 (2 pigs) by the Sabin-Feldman dye test. By the LAT, 5 pigs had a titer of <1:64 and by the IHAT all 11 pigs had a titer of <1:64. Antibodies (MAT titer, >1:25) were found in 31 (18.2%) of 170 feral pigs from mainland Georgia. This seroprevalence on the mainland was significantly higher (P < 0.0001) as compared on Ossabaw Island. The markedly low prevalence of T. gondii on Ossabaw Island was attributed to the virtual absence of cats on the Island; only 1 domestic cat was known to be present.